1. Technical Field
The present disclosure relates to a sewing machine which is provided with an engraving needle attached to a needle bar thereof and can execute an engraving work to form engraved marks by moving the engraving needle upward and downward while a workpiece is transferred in two predetermined directions by a transfer mechanism.
2. Related Art
There has conventionally been provided a multineedle embroidery sewing machine which can continuously execute embroidery sewing with the use of multicolor embroidery threads, for example. The embroidery sewing machine of this type is provided with a needle bar case which is mounted on a distal end of a sewing machine arm and has, for example, six needle bars. One of the needle bars is selectively coupled to a needle bar driving mechanism thereby to be vertically driven. The embroidery sewing machine is also provided with a transfer mechanism which transfers an embroidery frame holding a workpiece cloth. The embroidery sewing machine further includes a control device to which is supplied pattern data indicative of a needle location per stitch (an amount of movement of the workpiece cloth), color change and the like. The control device controls the needle bar driving mechanism and other driving mechanisms while controlling the transfer mechanism so that an embroidery frame holding the workpiece cloth is moved in two or X and Y directions, based on the supplied pattern data, whereby a multi-color embroidery sewing operation is executed.
The embroidery sewing machine of this type includes one provided with a boring device which makes a cut or bores a hole in the workpiece cloth. The boring device comprises a mount, a holder, a boring knife, a presser and a spring. The boring knife has a lower end formed with a blade portion. The boring device is attached to a specific one of needle bars and the operation of the embroidery sewing machine is started. As a result, eyelet embroidery is executable in which embroidery is made around a cut while the cut or the hole is being formed in the workpiece cloth.
On the other hand, a plurality of dents (embossment) or small holes has recently been formed in a sheet-like workpiece such as paper in a handicraft field, so that various types of patterns have been expressed using the dents or small holes. For example, a parchment craft has been becoming popular in which a plurality of dents or small holes is formed in thick tracing paper, which is formed into a decor. In this case, only the dents become cloudy when formed in the tracing paper. Patterns are made by utilizing the cloudy dents.
The inventors contemplated using a multineedle embroidery sewing machine as an apparatus which executes an engraving process to form the aforesaid dents or small holes by attaching an engraving needle for parchment craft, instead of the sewing needle. In this case, a holder to fixedly hold the sheet-like workpiece such as tracing paper is attached to a transfer mechanism, instead of an embroidery frame holding workpiece cloth. Based on generated engraving process data, a control device controls a needle bar to which the engraving needle is attached so that the engraving needle is moved upward and downward while the holder is moved by the transfer mechanism, whereby a predetermined engraving process is applied to the surface of the workpiece. Thus, various patterns each comprising a plurality of engraved marks or dents or small holes would be considered to be made.
A depth of engraving in the workpiece changes depending upon a mounting heightwise position of the engraving needle attached to the needle bar when the engraving process such as parchment craft or the like is executed by utilizing drive of the needle bar provided in the sewing machine. More specifically, the size of the engraved marks or dents or small holes to be formed on the workpiece changes. Accordingly, it has been sought that the mounting heightwise position of the engraving needle attached to the needle bar should be easily adjustable by the user. In this case, the size of an eyelet is changeable by adjusting the heightwise position of the boring knife relative to the holder in the conventional boring device.
The following work is considered to be done in order that the user may adjust the mounting height of the engraving needle relative to the needle bar. The user prepares a test workpiece to actually carry out a trial process, that is, an engraving process on the test workpiece. When visually observing an engraved mark, the user determines whether or not the size of the engraved mark is suitable, adjusting the mounting heightwise position of the engraving needle. In this case, the mounting heightwise position of the engraving needle is raised when the dent is excessively large. On the contrary, the mounting heightwise position of the engraving needle is lowered when the dent is excessively small. The aforementioned work is continued several times so that the mounting heightwise position of the engraving needle can finally be adjusted to a suitable position.
However, criterion for a determination as to whether or not the engraved mark has a suitable size depends upon the user's subjective view in the above-described adjusting manner. In particular, it is difficult for a user with less experience in the adjusting work to make a right determination. Furthermore, the adjusting work is troublesome since the trial process and the mounting heightwise position adjustment need to be carried out repeatedly. Additionally, the test workpieces are scrapped after having been used. Thus, since a large number of test workpieces are required, the test workpieces become useless.